diff --git a/app/seeders/admin_user_seeder.rb b/app/seeders/admin_user_seeder.rb
index f0ff1d4514fa..861e5e3fa7e9 100644
--- a/app/seeders/admin_user_seeder.rb
+++ b/app/seeders/admin_user_seeder.rb
@@ -27,10 +27,14 @@
 #++
 class AdminUserSeeder < Seeder
   def seed_data!
-    if Setting.seed_admin_user_enabled?
-      seed_admin!
+    user = new_admin
+    if user.save!(validate: false)
+      seed_data.store_reference(:openproject_admin, user)
     else
-      Seeder.logger.debug { "   *** skipped as explicity disabled with OPENPROJECT_SEED_ADMIN_USER_ENABLED" }
+      print_error "Seeding admin failed:"
+      user.errors.full_messages.each do |msg|
+        print_error "  #{msg}"
+      end
     end
   end
 
@@ -46,18 +50,6 @@ def not_applicable_message
     "No need to seed an admin as there already is one."
   end
 
-  def seed_admin!
-    user = new_admin
-    if user.save!(validate: false)
-      seed_data.store_reference(:openproject_admin, user)
-    else
-      print_error "Seeding admin failed:"
-      user.errors.full_messages.each do |msg|
-        print_error "  #{msg}"
-      end
-    end
-  end
-
   def new_admin # rubocop:disable Metrics/AbcSize
     User.new.tap do |user|
       user.admin = true
diff --git a/app/seeders/root_seeder.rb b/app/seeders/root_seeder.rb
index f1a150e4723f..0958652ca40c 100644
--- a/app/seeders/root_seeder.rb
+++ b/app/seeders/root_seeder.rb
@@ -75,6 +75,11 @@ def do_seed!
     seed_development_data if seed_development_data?
     seed_plugins_data
     seed_env_data
+    cleanup_seed_data
+  end
+
+  def cleanup_seed_data
+    admin_user.lock! if Setting.seed_admin_user_locked?
   end
 
   def seed_development_data?
diff --git a/app/seeders/seeder.rb b/app/seeders/seeder.rb
index ddda5866f47a..a9438416a45b 100644
--- a/app/seeders/seeder.rb
+++ b/app/seeders/seeder.rb
@@ -80,7 +80,7 @@ def not_applicable_message
 
   # The user being the author of all data created during seeding.
   def admin_user
-    @admin_user ||= (User.not_builtin.admin.first || User.system)
+    @admin_user ||= User.not_builtin.admin.first
   end
 
   protected
diff --git a/config/constants/settings/definition.rb b/config/constants/settings/definition.rb
index c3f71f87ed2f..8c7c30a1bd65 100644
--- a/config/constants/settings/definition.rb
+++ b/config/constants/settings/definition.rb
@@ -923,10 +923,10 @@ class Definition
         default: "https://releases.openproject.com/v1/check.svg",
         writable: false
       },
-      seed_admin_user_enabled: {
-        description: "Enable creating the admin user on first startup. " \
-                     "If set to false, an admin user has to be created manually.",
-        default: true,
+      seed_admin_user_locked: {
+        description: "Lock the created admin user after seeding, so it can not be used for logging in. " \
+                     "If set to true, an admin user has to be created manually or through an SSO provider.",
+        default: false,
         writable: false
       },
       seed_admin_user_password: {
diff --git a/modules/bim/spec/seeders/root_seeder_bim_edition_spec.rb b/modules/bim/spec/seeders/root_seeder_bim_edition_spec.rb
index d54b919a6832..92a37c492e51 100644
--- a/modules/bim/spec/seeders/root_seeder_bim_edition_spec.rb
+++ b/modules/bim/spec/seeders/root_seeder_bim_edition_spec.rb
@@ -250,33 +250,26 @@ def group_name(reference)
     include_examples "no email deliveries"
   end
 
-  context "when admin user creation is disabled with OPENPROJECT_SEED_ADMIN_USER_ENABLED=false",
+  context "when admin user creation is locked with OPENPROJECT_SEED_ADMIN_USER_LOCKED=true",
           :settings_reset do
     shared_let(:root_seeder) { described_class.new }
 
     before_all do
-      with_env("OPENPROJECT_SEED_ADMIN_USER_ENABLED" => "false") do
-        with_edition("bim") do
-          reset(:seed_admin_user_enabled)
+      with_env("OPENPROJECT_SEED_ADMIN_USER_LOCKED" => "true") do
+        with_edition("standard") do
+          reset(:seed_admin_user_locked)
           root_seeder.seed_data!
         end
       end
     ensure
-      reset(:seed_admin_user_enabled)
+      reset(:seed_admin_user_locked)
       RequestStore.clear! # resets `User.current` cached result
     end
 
-    it "creates the system user" do
-      expect(SystemUser.where(admin: true).count).to eq 1
-    end
-
-    it "does not create an admin user" do
-      expect(User.not_builtin.where(admin: true).count).to eq 0
-    end
-
-    it "seeds without any errors" do
+    it "seeds without any errors, but locks the admin user", :aggregate_failures do
       expect(Project.count).to eq 4
       expect(WorkPackage.count).to eq 76
+      expect(root_seeder.admin_user).to be_locked
     end
   end
 end
diff --git a/spec/seeders/admin_user_seeder_spec.rb b/spec/seeders/admin_user_seeder_spec.rb
index 2f567b4216ac..db1f4d1de5ef 100644
--- a/spec/seeders/admin_user_seeder_spec.rb
+++ b/spec/seeders/admin_user_seeder_spec.rb
@@ -39,18 +39,6 @@
     expect { seeder.seed! }.to change { User.admin.count }.by(1)
   end
 
-  context "when skipped with OPENPROJECT_SEED_ADMIN_USER_ENABLED=false",
-          :settings_reset,
-          with_env: {
-            OPENPROJECT_SEED_ADMIN_USER_ENABLED: "false"
-          } do
-    it "skips the creation" do
-      reset(:seed_admin_user_enabled)
-
-      expect { seeder.seed! }.not_to change { User.admin.count }
-    end
-  end
-
   context "when providing admin user seed variables",
           :settings_reset,
           with_env: {
@@ -68,6 +56,7 @@
       seeder.seed!
 
       admin = User.admin.last
+      expect(admin).to be_active
       expect(admin.firstname).to eq "foo"
       expect(admin.lastname).to eq "bar"
       expect(admin.mail).to eq "foobar@example.com"
diff --git a/spec/seeders/root_seeder_standard_edition_spec.rb b/spec/seeders/root_seeder_standard_edition_spec.rb
index b34d5ed7c88e..9f416a03afe6 100644
--- a/spec/seeders/root_seeder_standard_edition_spec.rb
+++ b/spec/seeders/root_seeder_standard_edition_spec.rb
@@ -287,33 +287,26 @@
     include_examples "no email deliveries"
   end
 
-  context "when admin user creation is disabled with OPENPROJECT_SEED_ADMIN_USER_ENABLED=false",
+  context "when admin user creation is locked with OPENPROJECT_SEED_ADMIN_USER_LOCKED=true",
           :settings_reset do
     shared_let(:root_seeder) { described_class.new }
 
     before_all do
-      with_env("OPENPROJECT_SEED_ADMIN_USER_ENABLED" => "false") do
+      with_env("OPENPROJECT_SEED_ADMIN_USER_LOCKED" => "true") do
         with_edition("standard") do
-          reset(:seed_admin_user_enabled)
+          reset(:seed_admin_user_locked)
           root_seeder.seed_data!
         end
       end
     ensure
-      reset(:seed_admin_user_enabled)
+      reset(:seed_admin_user_locked)
       RequestStore.clear! # resets `User.current` cached result
     end
 
-    it "creates the system user" do
-      expect(SystemUser.where(admin: true).count).to eq 1
-    end
-
-    it "does not create an admin user" do
-      expect(User.not_builtin.where(admin: true).count).to eq 0
-    end
-
-    it "seeds without any errors" do
+    it "seeds without any errors, but locks the admin user", :aggregate_failures do
       expect(Project.count).to eq 2
       expect(WorkPackage.count).to eq 36
+      expect(root_seeder.admin_user).to be_locked
     end
   end
 end
diff --git a/spec/seeders/seeder_spec.rb b/spec/seeders/seeder_spec.rb
index bd7a5003827a..2c9f0236abb1 100644
--- a/spec/seeders/seeder_spec.rb
+++ b/spec/seeders/seeder_spec.rb
@@ -37,16 +37,14 @@
 
   describe "#admin_user" do
     it "returns the admin created from the seeding" do
-      expect(seeder.admin_user).to eq(User.system)
-      expect { AdminUserSeeder.new(seed_data).seed! }.to change { User.admin.count }.by(1)
-      expect(seeder.admin_user).to eq(User.system)
-
-      expect(described_class.new.admin_user).to eq(User.not_builtin.admin.first)
+      expect(seeder.admin_user).to be_nil
+      AdminUserSeeder.new(seed_data).seed!
+      expect(seeder.admin_user).to be_a(User)
     end
 
     it "does not return the system user" do
       expect { User.system }.to change { User.admin.count }.by(1)
-      expect(seeder.admin_user).to eq(User.system)
+      expect(seeder.admin_user).to be_nil
     end
   end
 end